Tablet disintegration apparatus

ABSTRACT

THIS INVENTION PROVIDES AN IMPROVEMENT IN A TABLET DISINTEGRATING APPARATUS, BY PROVIDING A PLURALITY OF OPPOSED SPACED ELECTRODES AT THE BASE OF THE TABLET CONTAINING TUBES. IN THE OPERATION OF THE APPARATUS AN ELECTRIC FIELD IS SET UP BETWEEN THE ELECTRODES. THE PRESENCE OF A TABLET DISTURBS THIS ELECTRIC FIELD, WHICH DISTURBANCE ACTUATES A RECORDING DEVICE SUCH AS A TIMER. THE CONVENTIONAL RECIPROCATING VERTICAL MOTION OF THE APPARTUS (IN AN AQUEOUS BATH) CAUSES THE TABLET TO DISINTEGRATE. AT THE END POINT OF THE TABLET DISINTEGRATION, THE UNDISTURBED FLOW OF CURRENT BETWEEN THE ELECTRODES STOPS THE RECORDING DEVICE, NOTING THE INTERVAL OF TIME FOR TABLET DISINTEGRATING

Nov. 9, 1971 G- W. MELLIGER' TABLET DISINTEGRATION APPARATUS 2 Sheets-Sheet 1 Filed April 9, 1970 POWER AND MONITORING UNIT FIG. 3

FIG.

FIG. 5

lNV NTOR Gu|do W Melllger B 2M /y ATTORNEY Nov. 9, 197] G- W. MELLIGER 3,618,395

TABLET DISINTEGRATION APPARATUS Filed April 9, 1970 2 Sheets-Sheet :1

FIG. 6

OSCILLATOR AMPLIFIER I DEMODULATION RECORDER SWITCH SIGNAL FILTER TIMER FIG. 7

INVENTORI Guido W. MeIIiger By M am ATTORNEY United States Patent US. Cl. 73-432 Claims ABSTRACT OF THE DISCLOSURE This invention provides an improvement in a tablet disintegrating apparatus, by providing a plurality of opposed spaced electrodes at the base of the tablet containing tubes. In the operation of the apparatus an electric field is set up between the electrodes. The presence of a tablet disturbs this electric field, which disturbance actuates a recording device such as a timer. The conventional reciprocating vertical motion of the apparatus (in an aqueous bath) causes the tablet to disintegrate. At the end point of the tablet disintegration, the undisturbed flow of current between the electrodes stops the recording device, noting the interval of time for tablet disintegration.

This invention relates to tablet disintegration testing. More particularly, it relates to improvements in an apparatus for determining the disintegration time of tablets.

In many instances, the efficacy of a pharmaceutical tablet is dependent on its disintegration time. Tablets that distintegrate too rapidly or too slowly may not supply the medicament to the patient at the desired time interval. It is therefore important that the tablet formulator know the disintegregation time of the various tablet batches being prepared.

Various prior art apparatus are available to determine disintegration time of tablets. Basically, these apparatus consist of glass or Plexiglas tubes mounted vertically in a rack. The upper end of the tube is open and the lower end is closed by a screen of predetermined size. A tablet is placed in a tube, the rack immersed in an aqueous bath and is mechanically lifted up and down. The action of the bath fluid upon the tablet, together with the tablet periodically striking the wire mesh, causes the tablet to disintegrate. The end point of the tablet disintegration is determined by the operator, when he notes the absence of a definable tablet segment. It is in the end point determination that the prior art apparatus are deficient. For, as a typical tablet disintegrates, the bath may become cloudy with tablet particles, and it is difiicult for the observer to note the precise point at which the tablet has disintegrated.

It is therefore an object of this invention to provide an improvement in a tablet disintegration apparatus which is automatic in operation and which precisely determines the end point of a tablet distintegration without the presence of an observer.

It is also an object of this invention to provide a method for determining the disintegration point of a tablet without the presence of an observer.

These and other objects of the invention will become apparent from the following detailed description and drawings, wherein:

FIG. 1 is an isometric front view of typical basket-rack assembly of this invention;

FIG. 2 is a sectional view of a typical basket of this invention on the line 2-2 in FIG. 1;

FIG. 3 is a view of the basket of FIG. 2 showing electrical field;

FIG. 4 is a view of the basket of FIG. 2 showing a preferred embodiment of this invention;

FIG. 5 is a view of the basket of FIG. 2 showing an additional embodiment of this invention;

FIG. 6 is a view of the basket of FIG. 2 showing a further embodiment of this invention; and

FIG. 7 is a schematic diagram of the process and monitoring unit of FIG. 1.

Basically this invention provides an improvement in a tablet disintegrating apparatus by having a plurality of opposed spaced electrodes at the base of the tablet containing tubes. In the operation of the apparatus an electric field is set up between the electrodes. The presence of a tablet disturbs this electric =field, which disturbance actuates a recording device such as a timer. The conventional reciprocating vertical motion of the apparatus (in an aqueous bath) causes the tablet to disintegrate. At the end point of the tablet disintegration, the undisturbed flow of current between the electrodes stops the recording device, noting the interval of time for tablet disintegration.

This invention will be best understood from a detailed description of the apparatus of this invention and its use in tablet disintegration testing.

Referring now to FIG. 1, there is depicted a typical basket rack assembly generally at 10, capable of holding a plurality of baskets one of which is shown at 11. The apparatus of this invention is applicable to more than one basket '11, however, a description of one is sufiicient to an understanding of the invention, and is not a limitation of the invention. At the base of basket 11 are opposed spaced electrodes 13 and 14- (see FIG. 1). A screen 12 allows tablet particles to pass out of the basket 11. Electrodes 13 and 14 are connected to a suitable power and monitoring unit 18 by means of wires 16 and 17. In a preferred embodiment of this invention the electrodes 13 and 14 are mounted on the screen 12 as illustrated in FIG. 4. The screen 12 may be a conductor or a nonconductor; however, if it is a conductor such as stainless steel, the electrodes 13 and '14 are insulated from the screen 12. The screen 12. may be in any shape desired, e.g., circular, square, etc. The mesh size of the screen 12 is not critical and is determined by the specifications of the test method employed in the tablet disintegration testing.

In the operation of this invention, a tablet 21 is placed in the basket 11 in the basket rack assembly 10. The assembly 10 is attached by means of shaft 22 to an integral power unit (not shown). The assembly 10 is then immersed in an aqueous bath and the integral power unit turned on to provide a vertical up and down movement of the assembly 10' in the bath. The power and monitoring unit 18 (which is independent of the integral power unit) is simultaneously turned on to activate both a recording device and the electrodes 13 and 14 which sets up the electric field 19 (see FIG. 3). The tablet 21 disturbs the electric field 19, which disturbance is monitored by unit 18. The electric field 19 is thus disturbed until the tablet 21 is disintegrated by the movement of the bath fluid through assembly 10. At the point of disintegration of the tablet 2.1, the electric field 19 is again undisturbed. This undistunbed current flow between electrodes 13 and 14 is monitored by unit 18, which is indicated on the recording device.

It is also a preferred embodiment of this invention to afiix a shield 23 beneath the electrodes 13 and 14. This is shown in FIG. 4. The shield 23 both protects the electrodes 13 and 14 from damage (when mounted on screen 12) and also prevents objects other than the tablet being tested from disturbing the signal from the electrodes 13 and 14. It will be appreciated by one skilled in the art that the electric field 19 also flows beneath the screen 12 (if screen 12 is a non-conductor) and can register the presence of materials such as tablet particles passing through it. The shield 23 prevents interference with the current flow beneath the screen 12. The shield 23 is a conductor and can be constructed of any suitable material such as metal coated plastic or stainless steel. The shield 23 is affixed to the screen 12, by any suitable means at a point on points outside of the wall of basket 11, as shown at 24 and 26 in FIG. 4. The shield 23 should be of sufficient size to cover the base opening of tube 11. The shield 23 should be in close proximity to the screen 12, but the space between shield 23 and screen 12 should be such as to permit the passage of the particles of the tablet from the tube 11 through screen 12 into the bath and should not interfere with the bath flow in the basket 11. The apparatus of this invention can be used in standard tablet disintegration testing procedures such as U.S.P. XVII (pp. 919-921) and NF. XII (pp. 501-502).

Average current in the electric field 19 can vary depending upon the bath conditions. For example, the electric current through distilled water would be different than that through a 0.1 N hydrochloric acid solution. To compensate for current differences between different test baths, a third electrode 27 may be introduced between the electrodes 13 and 14. Electrodes 13, 14 and 27 thus form a compensated half bridge. Electrode 27 is connected to the power and monitoring unit 18 by wire 28. This is illustrated in FIG. 5.

Certain tablets because of their composition are resistant to disintegration in the test procedure described above. The procedure can be modified (U.S.P. XVII, pp. 919, 920) by placing a plastic disc above the tablet. As the basket-rack assembly moves up and down, the disc strikes the tablet accelerating the tablets disintegration. At the end point of the tablet disintegration, however, the disc iself will disturb the electric field, and thus interfere with the power and monitoring units detection of the end point of the tablet disintegration. It is a further embodiment of this invention to provide a fourth electrode 29 at the base of the basket 11 (see FIG. 6), to compensate for the interference of disc 31 with the electric field. Together with electrode 27, electrode 29 measures the strength of the electric field introduced by electrodes 13 and 14. With the disc 31 at the base of basket 11, the strength of the electric field produced by electrodes 13 and 14 approaches Zero. This extreme diminution of field strength indicates that only the disc 31 is disturbing the electric field and that tablet 21 has disintegrated. Electrode 29 may be between electrodes 13 and 27 or between electrodes 14 and 27, and is connected to unit 18 by wire 32.

It is understood that the embodiments described using electrodes 13, 14 and 27 and electrodes 13, 14, 27 and 29 can be used with the shield 23 affixed to the basket 11.

The power and monitoring unit 18 of this invention is conventional and may be assembled by one skilled in the art. Typically, it may consist, in combination, of an oscillator for the carrier frequency, carrier frequency amplifier, signal rectifier, signal filter and switch. A timer, recorder or counter is inserted within the circuit described, to record the tablet disintegration. The power and monitoring unit 18 is schematically represented in FIG. 7.

The oscillator supplies alternating current, maintaining an unhomogeneous electric field between the electrodes with a carrier frequency high enough to give sufficient resolution of the resistance changes in the electrode system. The advantage of alternating current over direct current is the elimination of uncontrollable polarization effects. The amplifier increases the small, modulated carrier frequency signal derived from the electrode system. Demodulation is the rectification of the amplified, modulated carrier frequency signal in order to separate the modulation content. The filter accomplishes two things (a) the complete elimination of the carrier frequency from the signal by use of frequency dependent filters; and (b) differentiation of the signal. The signal consists of low frequency electric pulses which represent the change of resistance in the electrode system, due to the presence of a non-conducting solid material (tablet) moving in the unhomogeneous electric field. The timer delivers pulses at desired intervals, e.g., one second. The switch disconnects the recorder or counter from the timer, as soon as the signal disappears. The recorder accumulates the pulses that are received from the timer.

It will be appreciated that as a tablet is in the final stages of disintegration, the tablet particle may alight upon the electrode 27 and interfere with its function. To avoid this occurrence, it is desirable that the fluid flow through the basket 11 be non-laminar. A non-laminar flow can be assured, e.g., by replacing the screen 12 with a non-conducting plate, having a plurality of passageways through it, which passageways are set at an angle to the horizontal surface of the plate. The fluid therefore as it passes through the basket 11 has a non-laminar motion imparted to it. It will also be appreciated that the size and number of the passageways should be such that the flow of fluid through basket 11 is substantially the same as with the screen 12. Other means of achieving a nonlaminar flow through basket 11 will be readily apparent to those skilled in the art.

This invention is also adaptable to indicating the various stages of a tablets disintegration. This is accomplished by monitoring the degree of disturbance of the electric field introduced by the electrodes as a tablet passes through the various stages of disintegration.

What is claimed is:

1. An apparatus for determining the disintegration of a tablet which comprises a plurality of opposed spaced electrodes within a tablet basket, said electrodes adapted for use with actuating and monitoring means.

2. In an apparatus for determining the disintegration of a tablet, comprising in combination a tablet basket, basket rack assembly, a screen at the base of said basket, the improvement which comprises, a plurality of opposed spaced electrodes at the base periphery of said basket wall, said electrodes adapted for use with actuating and monitoring means.

3. The apparatus according to claim 2, having a shield spaced from and below said screen said shield being attached to said screen by a plurality of attaching means, said attaching means being outside the periphery of said tube wall.

4. In an apparatus for determining the distintegration of a tablet, comprising in combination a tablet basket, basket rack assembly, a screen at the base of said basket, the improvement which comprises, a plurality of opposed spaced electrodes mounted on said screen at the periphery of said basket wall.

5. The apparatus according to claim 4, having a shield spaced from and below said screen, said shield being attached to said screen by a plurality of attaching means, said attaching means being outside the periphery of said tube wall.

6. In an apparatus for determining the disintegration of a tablet, comprising in combination a tablet basket, basket rack assembly, a screen at the base of said basket, the improvement which comprises a plurality of opposed spaced electrodes at the base periphery of said basket wall, a means for actuating said electrodes, and means for recording disturbances in the electric field between said actuated electrodes.

7. The apparatus according to claim 6, having ashreld spaced from and below said screen, said shield being attached to said screen by a plurality of attaching means, said attaching means being outside the periphery of said tube wall.

8. A method for determining the end point of the disintegration of a tablet, which comprises, monitoring the disturbance of an electric field by said tablet and recording the absence of said disturbance at the disintegration point of said table.

9. A method for determining the end point of the disintegration of a tablet, which comprises placing a tablet basket in a basket rack assembly, actuating said assembly in a reciprocating vertical motion to elfect tablet disintegration, monitoring said table disintegration by the disturbance of the electric field at the base of said tablet basket, and recording the absence of the disturbance of said electric field at the disintegration point of said tablet.

10. A method for determining the end point of the disintegration of a tablet, which comprises placing a 10 tablet in a tablet basket in a basket-rack assembly, placing a plastic disc above said tablet in said basket, actuating said assembly in a reciprocating vertical motion to effect said tablet disintegration, monitoring said tablet disintegration UNITED STATES PATENTS 3/ 1966 McKeoWn 73-86 7/ 1965 Simoons 73432 SI S. C. SWISHER, Primary Examiner U.S. C1. X.R. 324-71 

